30 December 1942

          1.    OBJECT:

                 To determine the relative tactical value of the P-51 type fighter aircraft for combat service.

          2.    INTRODUCTION:

                 This test was authorized by letter from Headquarters Army Air Forces, Director of Air Defense, dated July 13, 1942, to Commanding General, Air Forces Proving Ground, Eglin Field, Florida, subject: "Test of P-51 Airplanes." This test was started August 7, 1942, and was finished November 1, 1942.

                 a.    Description.    The articles tested are P-51 type airplanes, Air Corps Serial Nos. 41-37323, 41-37324, and 41-37325.

          3.    CONCLUSIONS:

                 It is concluded that:

                 a.    The subject aircraft is the best low altitude American fighter aircraft yet developed, and should be used as the criterion for comparison of subsequent types.

                 b.    If possible, the power loadings of this fighter aircraft should be materially reduced, without increasing the wing loading.

                 c.    To reduce the power loadings of the aircraft, excess weight in the structure, and accessories not vital to operational use should be eliminated, and engine performance increased.

                 d.    Pilots become completely at home in this aircraft immediately after the first take-off due to the remarkable sensitivity of control, simplicity of cockpit, and excellent flying characteristics.

                 e.    The rate of roll is not as rapid as is desired for combat operations.

                 f.    The view downward over the nose is not sufficient to allow full deflection shooting in a turn.

                 g.    The automatic manifold pressure regulator is completely satisfactory.

                 h.    With the exception of the radiators, the airplane is completely satisfactory.

                 i.    The range of speeds obtainable in the throttle limits in level flight is excellent.

                 j.    Up to fifteen-thousand (15,000) feet this is faster than all standard American fighters with the exception of the P-47C-1.

          4.    RECOMMENDATIONS:

                 It is recommended that:

                 a.    The subject aircraft be equipped with an engine which will permit satisfactory tactical combat maneuvering between twenty-five-thousand (25,000) and thirty-thousand (30,000) feet.

                 b.    The present armament in the subject aircraft be changed from four (4) 20 mm cannon to four (4) .50 caliber machine guns, wing mounted, and that these be high cyclic rate of fire guns when conclusive tests are accomplished with the guns and standardization is effected.

                 c.    Provisions be provided for carrying external combat and ferrying fuel tanks.

                 d.    The subject aircraft be equipped with the modified N-7 type gun sight to allow changing of bulb while in flight and to set dropping angle for low level bombing.

                 e.    The subject aircraft be equipped with the Stoddard radio (Model MRT-3A) for test at this station. This radio weighs forty-six (46) pounds installed.

                 f.    The brakes of the subject aircraft be redesigned for more satisfactory operation.

                 g.    The throttle and propeller controls be hooked together to operate as a unit, if the pilot desires.

                 h.    The coolant and oil radiators be redesigned for more satisfactory service, and the mountings be modified to permit much faster installation and removal.

                 i.    Study be made of canopy structure to determine the weakness which allows the canopy to bulge at high speed, and steps be taken to correct this condition.

                 j.    The subject aircraft be equipped with an automatic shutter control (factory has installation).

                 k.    It be equipped with a stick locking tail wheel (factory has installation).

                 l.    It be equipped with more effective aileron control to produce higher rate of roll at all speeds (factory has installation).

                 m.    It be equipped with left wing landing light only.

                 n.    It be equipped with a "Demand" oxygen system (now standard equipment).

                 o.    The electrical compass indicator magnesyn remote indicating compass be installed.

                 p.    The automatic manifold pressure regulator be incorporated on all subsequent models of this airplane.

          5.    RECORD OF TEST:

                 This test was conducted according to the Test Program, Proof Department, No. 4-42-7, this headquarters, dated August 3, 1942, a copy of which is attached as Inclosure No. 1, except for the procedure called for in paragraph 3 a (4). This portion of the test has not been completed.

          6.    DISCUSSION:

                 a.    Performance.    For speed, rate of climb, range and gas consumption tables, see Inclosure No. 2.

                 b.    Maneuverability.    The subject aircraft was flown in "mock" combat against the P-38F, P-39D, P-40F, P-47B, and the Mitsubishi "00" type of aircraft.

                 c.    The following results were obtained:

(1)    The subject aircraft was found to be superior in speed of the Mitsubishi "00", P-39D, P-47F at all altitudes and the P-47B and P-38F up to fifteen-thousand (15,000) feet.
(2)    The subject aircraft was found to be superior in rate of climb to the P-39D, P-40F, and the P-47B up to fifteen-thousand (15,000) feet.
(3)    The acceleration in dives and the maximum permissible diving speed of the subject aircraft is superior to all types tested.
(4)    The turning characteristics of the subject aircraft are substantially the same as the P-40F and the P-39D. None of these appears to have any definite superior turning characteristics.
(5)    In close "dog fighting" the subject aircraft has the very decided advantage of being able to engage or break off combat at will. However, if neither airplane attempts to leave the combat, the P-40F is considered to have a slight advantage.

                 d.    Ceiling.    The absolute ceiling of the subject aircraft at the date of this report was found to be approximately thirty-one-thousand (31,000) feet. It is believed that the fighting ceiling of this aircraft is twenty-thousand (20,000) feet as the engine loses power very rapidly above eighteen-thousand (18,000) feet. This limited ceiling is the most serious handicap to this aircraft, and every effort should be made to increase the power and critical altitude of the engine.

                 e.    Range.    The cruising ranges of the subject aircraft are contained in Inclosure No. 2.

                 f.    Flying Characteristics – General.   

(1)    The flying characteristics of the P-51 are exceptionally good and the aircraft is very pleasant and easy to fly. Its taxiing visibility is limited in view over nose as are all standard landing gear fighters having engine in front of pilot. There is no objectionable amount of torque on take-off and the ship becomes air-borne very nicely. A pilot flying this plane for the first time feels immediately at home when this ship leaves the ground, and he has a feeling that he has flown this ship for a large number of hours. The plane picks up speed very rapidly after leaving the ground and will climb equally well between one-hundred-sixty-five (165) miles per hour and two-hundred-five (205 miles per hour I.A.S. This ability to climb well at a high indicated speed should be a great aid in helping catch targets having altitude and attempting to escape. In level flight trimmed up, the aircraft will fly practically hands off. There is a speed range of about two-hundred (200) miles difference in which it is possible for the pilot to control plane without aid of trim. The plane handles nicely in a dive, using a very small amount of trim, and accelerates faster than any other type American fighter. At five-hundred (500) miles indicated with small aid from the trim tabs, the plane still maintains its stability. In normal flight, the plane responds quickly to the controls, however, the aileron roll is slower than desired and tightens at very high speeds. It is very easy to put through all normal acrobatics, and it has sufficient speed to perform all these acrobatics from level flight without diving to pick up speed. At slow speeds when approaching the field for a landing, there is a mushy feeling in the aileron but the control is still there. The plane lands nicely, has a tendency to skip several times if landed fast, and it rolls in a straight line without attempting to swing or break noticeably in either direction.

                 g.    Cockpit Arrangement.    The engine and flight controls of the subject airplane are conventional. A drawing for an improved for an improved instrument panel is submitted as Inclosure No. 3.

                 h.    Armament.

(1)    The present armament is considered adequate, but is functionally unsatisfactory. It is believed that four (4) caliber .50 (high rate of fire) guns would furnish ideal fire power for the P-51 airplane.
(2)    The present N-3A gun sight should be replaced with the N-7 type sight in order to permit changing of the bulb while in flight.

                 i.    Armor.

(1)    The pilot is covered from behind by armor plane one-fourth (1/4th) inch thickness and in front by the engine and a bulletproof glass panel.
(2)    All fuel tanks are self-sealing.

                 j.    Vulnerability of vital installations.

(1)    The engine and oil tank are mounted in the nose of the subject aircraft and are not considered as vulnerable as those mounted to the rear of the cockpit.
(2)    The coolant and oil radiators are combined into one (1) assembled unit and are located in the belly of the aircraft just behind the cockpit. For the reason that most hits on an airplane in combat are to the rear of the cockpit, it is believed that this radiator installation may prove to be quite vulnerable. It is recommended that the designer of the subject aircraft make a study of the possibilities of incorporating a sheet of armor plate to protect the radiator from fire from the rear.

                 k.    Visibility.

(1)    The pilot’s visibility is in general very similar to that afforded him in the P-40 type aircraft. The view to the rear is somewhat restricted but not dangerously so.
(2)    The visibility forward in flight attitude is good except over the nose, but on the ground is extremely poor.
(3)    Every effort must be made to increase the angle of view over the nose. At present the view over the nose is restricted to 3° 4’ below the sight line. A mirror arrangement to increase angle of view should be developed.

                 l.    Night Flying.    The subject aircraft is suitable for night flying, but because of the very restricted view forward, it is a bit difficult in the run after landing.

                 m.    Instrument Flying.    The subject airplane due to its excellent stability is easily flown by the use of instruments.

                 n.    Speed of Servicing.    The subject aircraft can be completely serviced (fuel, coolant, oxygen, ammunition, and radio check) in five (5) minutes by a crew consisting of the following:

                 Four (4) armorers, two (2) mechanics, and one (1) radioman.

                 o.    Maintenance.    The regular fifty (50) hour inspection can be completed in approximately eight (8) hours by using the optimum crew, or it can be completed in approximately ten (10) hours by a crew of two (2) men. The most common maintenance difficulties were found to be:

(1)    Radiator leakage and the time required to remove and install the radiator unit is unsatisfactory. It is believed by maintenance crew, that most leaks in the radiator are due to poor workmanship rather than faulty design.
(2)    Considerable trouble was experience with brake action. It is recommended that both deficiencies be corrected.
(3)    In order to change magneto, retime or change points, carburetor airscoop must be removed. It is recommended than, if possible, the carburetor airscoop be redesigned to give more room for working on the magneto.
(4)    Cuno strainers are too difficult to remove and install.
(5)    Larger inspection planes for fuel tank sump drain are desired.
(6)    Separate drains for supercharger section, distributor section, and coolant pump are desired.

          7.    INCLOSURES:

                 Inclosure No. 1 - Test Program.
                 Inclosure No. 2 – Speed, Rate of Climb, Range, and Gas Consumption Tables.
                 Inclosure No. 3 – Drawing.

Main    P-51 Performance (Allison Engine)